1. Field of the Invention
The invention relates to nanotechnology-based devices and, more specifically, to nanobelts, nanorods, nanopropellers and devices made therefrom.
2. Description of the Related Art
Binary semiconducting oxides often have distinctive properties and can be used as transparent conducting oxide (TCO) materials and gas sensors. Current studies of semiconducting oxides have been focused on two-dimensional films and zero-dimensional nanoparticles. For example, fluorine-doped tin oxide films are used in architectural glass applications because of their low emissivity for thermal infrared heat. Tin-doped indium oxide (ITO) films can be used for flat panel displays (FPDs) due to their high electrical conductivity and high optical transparency; and zinc oxide can be used as an alternative material for ITO because of its lower cost and easier etchability. Tin oxide nanoparticles can be used as sensor materials for detecting leakage of several inflammable gases owing to their high sensitivity to low gas concentrations.
In contrast, investigations of wire-like semiconducting oxide nano structures can be difficult due to the unavailability of nanowire structures. Wire-like nano structures have attracted extensive interest over the past decade due to their great potential for addressing some basic issues about dimensionality and space confined transport phenomena as well as related applications. In geometrical structures, these nanostructures can be classified into two main groups: hollow nanotubes and solid nanowires, which have a common characteristic of cylindrical symmetric cross-sections. Besides nanotubes, many other wire-like nanomaterials, such as carbides, nitrides, compound semiconductors, element semiconductors, and oxide nanowires have been successfully fabricated.
However, the nanostructures discussed above can have a variety of deficiencies. For example, often it is difficult to control the structure and morphology of many nanostructures. Further, many nanostructures are not defect and/or dislocation free. These deficiencies can cause problems such as, for example, uncontrolled properties due to uncontrolled structure and morphology, scattering from dislocations in electric transport applications, and degraded optical properties.
Semiconducting oxides, as an important series of materials candidates for optoelectronic devices and sensors, have attracted considerable attention in scientific research and technological applications. Recently, quasi-one-dimensional nanostructures for the functional materials have been successfully fabricated by using various approaches including thermal evaporation, sol-gel, arc discharge, laser ablation and template-based method. To date, extensive research work has been focused on ZnO, which is one of the most useful oxides for optical and sensor applications. Many different morphological ZnO nanostructures, including wires, belts, and rods, etc., have been fabricated.
In ZnO, a combination of the three types of fast growth directions ([2 1 10], [01 10], and [0001]) and the three area-adjustable facets [2 1 10], [01 10], and [0001]) of ZnO has resulted in a diverse group of hierarchical and intricate nanostructures. In addition to non-central symmetry, the semiconducting and piezoelectric as well as surface polarization characteristics of ZnO make it one of the most exciting oxide nanostructures for investigating nano-scale physical and chemical properties. Structural configurations such as piezoelectric nanobelts, nanosprings, and nanorings, etc., are known.
Cantilever based scanning probe microscopy (SPM) techniques are among the most powerful approaches for imaging, manipulating and measuring nanoscaled properties and phenomena. SPM's generate images by measuring forces between sample surfaces and microscope probes. Common forces detected using SPM's are the van der Waals force, electrostatic force, capillary force, and double-layer force. Conventional SPM cantilevers are fabricated from silicon, SiC and Si3N4 using e-beam or optical lithography. A typical SPM cantilever has a length, width, and thickness of about 125 μm, about 35 μm, and about 4 μm respectively. The resolution of an SPM is limited by three factors; 1) the shape of the tip, 2) the sample-tip contact, and 3) the ability to measure the sample-tip interaction.
Ideally an SPM probe would be a robust one-dimensional structure, while the cantilever would poses ultra-high sensitivity to any and all forces. Atomic force microscope tips have been developed by growing carbon nanotubes on the ends of standard AFM probes. These high aspect ratio tips are nearly ideal for AFM imaging because of their size and durability. As a result, the nanotubes can image surfaces with a large degree of abrupt variation in surface morphology. Geometrically small single crystal silicon cantilevers are being developed in an attempt to measure the electronic spin of materials. The capabilities of nanotube tips will not be fully exploited until the cantilever is sensitive to all nanotube-surface interactions, nor can imaging of electronic spin occur until measurements of forces in the sub-atom Newton range become a reality.
Numerous applications will require controlled movement of fluids at the nano scale. For example, some proposed lab-on-a-chip designs will need to be able to monitor fluid flow, induce movement and mix fluids at the nano scale.
Therefore, there is a need for defect and dislocation free nano structures.
There is also a need for a method of sensing and inducing fluid flow at the nano scale.